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Safety Evaluation of Permanent Raised Pavement Markers (2004)

Chapter: Chapter 1 - Introduction

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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2004. Safety Evaluation of Permanent Raised Pavement Markers. Washington, DC: The National Academies Press. doi: 10.17226/13724.
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3CHAPTER 1 INTRODUCTION Fifty-seven percent of the 37,795 fatal crashes in the United States during 2001 occurred on two-lane undivided high- ways, compared with just 6.1 percent of fatal crashes that occurred on four-lane divided highways (1). Over one-third of the fatal crashes on two-lane undivided highways and 27 percent of the fatal crashes on four-lane divided highways occurred during dark or unlighted conditions. The majority of those crashes involved only one vehicle. Any safety mea- sure that has the potential to increase visibility and assist drivers in staying within their lanes should therefore be given serious consideration. Pavement markings and other delineation devices provide drivers with information about their position within their own lane and information about which lanes are available for their use, especially at night. In addition, delineation devices pro- vide the driver with a preview of upcoming changes in the roadway geometry, including curves, lane drops, narrowing, the start and end of passing zones, crosswalks, and intersec- tions. Permanent raised pavement markers (PRPMs) are delineation devices that are often used for centerline, lane divider line, and, more rarely, edgeline applications to improve preview distances and guidance for drivers in inclement weather and low-light conditions. Recent studies in New York, Texas, and Pennsylvania, which are discussed in Chapter 2, have raised concerns about the safety effects of PRPMs after potential negative side effects were reported. These studies are among the few that have been performed to date to determine the effect of PRPMs on highway safety. These studies pertained to single juris- dictions only, and their results were questionable because of some data and methodological difficulties. NCHRP Project 5-17 responded to the need to use state-of-the-art analytical methods and comprehensive data to assess the safety effects of PRPMs and to identify critical design parameters. The pri- mary objectives of NCHRP Project 5-17, as presented in the project statement, were “to assess the safety effects of per- manent raised pavement markers (PRPMs) and to develop guidelines for their use.” To achieve these objectives, data related to snowplowable PRPM, nonintersection locations along two-lane roadways, four-lane divided expressways, and four-lane freeways road- ways from six U.S. states (Illinois, Missouri, Pennsylvania, New York, Wisconsin, and New Jersey) were collected, aim- ing to undertake a statistically defendable analysis of their crash experience. The six states were selected after undertaking a detailed survey of PRPM implementation practices and an assessment of data availability (to support a safety evaluation of PRPMs) in 29 U.S. states with known PRPM installations. A review of literature pertaining to past research on the safety effect of PRPMs and a survey of current PRPM imple- mentation practices were undertaken during the first quarter of 2002. The literature review identified critical design param- eters, data requirements, methodological issues, and chal- lenges. These were carefully studied before the formulation and implementation of the study design. A literature review of the human factor issues pertaining to PRPMs was executed. The knowledge from these past research studies was used in the interpretation of the safety evaluation results and the development of PRPM implemen- tation guidelines. Two types of safety data analyses were performed: (1) a composite analysis that determined the overall effect of PRPMs, by state, for a number of different crash types (e.g., nighttime, wet weather, and guidance) and (2) a disaggregate analysis that investigated the relationships between the safety effect of PRPMs on nighttime crashes and a number of critical roadway, traffic, and PRPM design parameters. The results of these analyses were used to develop, in combination with human factors considerations, a comprehensive set of guide- lines for the application of PRPMs, as well as an engineering procedure for estimating the anticipated cost-effectiveness of PRPMs at a particular location. The body of this report has been structured into six addi- tional chapters: the findings from the review of the PRPM- related literature and jurisdictional practices (Chapter 2), data collection and preparation (Chapter 3), safety impact analy- sis of PRPM installations (Chapter 4), a discussion of study results (Chapter 5), guidelines for the use of snowplowable PRPMs (Chapter 6), and study conclusions (Chapter 7).

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 518: Safety Evaluation of Permanent Raised Pavement Markers examines the safety performance of snowplowable permanent raised pavement markers on two-lane roadways and four-lane freeways.

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